Dicarboxylic Acid Catabolism by Bacteria

Abstract

establish that the exchange of hydrogen atoms between water and deoxyadenosylcobalamin is an integral part of the reductase reaction the following facts are consistent with this view. Both the exchange reaction and the overall reduction of ribonucleotides have an essential requirement for dihydrolipoate. Further, deoxyribonucleotides that accelerate the reduction of specific ribonucleotides also cause much greater exchange to occur than that in the absence of nucleotides. The two reactions are catalysed by the same highly purified enzyme, and treatment of the enzyme preparation with protein reagents such as 1-fluoro-2,4-dinitrobenzene, N- bromosuccinimide and N-acetylimidazole decreases the rate of ribonucleotide reduction and of the exchange reaction to approximately the same extent. Finally, rate calculations show that the rate of the exchange reaction is comparable with that of ATP reduction under similar conditions. From these preliminary experiments it appears possible that deoxyadenosylcobalamin participates in hydrogen transfer between dihydrolipoate and the nucleotide substrate.